1. Field of the Invention
The present invention relates to a vehicle wheel driving apparatus and an electric motor which includes bearings and bearing mounting portions.
2. Description of Related Art
A vehicle wheel driving apparatus has a bearing, so that the bearing functions to reduce friction and receive reaction force when a component such as a hub is rotated. For example, there is a rolling bearing which is used to support a drive shaft of a vehicle (refer to, for example, Japanese Patent Unexamined Publication Document JP-A-2002-321665).
The JP-A-2002-321665 will be described based on the following drawing.
FIG. 6 is a drawing which explains a basic configuration of a technique according to the related art, and a related-art rolling bearing 201 supports a one end 204 side of a drive shaft 203, and a related-art rolling bearing 205 supports the other end 206 of the drive shaft 203.
The rolling bearings 201, 205 both have a general configuration (for example, refer to the Japanese Industrial Standard (JIS) number: JIS B0104) and each include an inner ring 207, an outer ring 208 and rolling elements 209 . . . ( . . . denotes the plurality. This will be true hereinafter). By disposing the rolling bearings 201, 205 apart from each other by a distance y, the weight of a final gear 211 and reaction force of driving force of the final gear can be supported between the rolling bearings 201, 205, thereby making it possible to enhance strength necessary to support the drive shaft 203.
In the rolling bearings 201, 205 used on the drive shaft 203 of the vehicle 202 in the JP-A-2002-321665, however, due to the rolling bearing 201 and the rolling bearing 205 being spaced apart from each other by the distance y, points of application of load need to be set at the distance y, whereby the construction in the axial construction of the drive shaft 203 tends to be enlarged. A rolling bearing has been in demand which can realize a reduction in size in the axial direction.
The JP-A-2002-321665 also describes an electric motor for driving a vehicle of the related art.
FIG. 14 is a drawing which explains a basic configuration of a technique according to the related art, and a related-art electric motor 1202 for driving a vehicle 1201 and is constructed such that an output end 1204 side of an output shaft 1203 of the electric motor 1202 is supported by a bearing 1205. A bearing portion 1206 is formed on the output end 1204 side into which the bearing 1205 is fitted, and a fitting hole 1208 is formed in a motor case 1207 into which the bearing 1205 is fitted, whereby the output shaft 1203 of the electric motor 1202 for driving the vehicle 1201 can be supported.
In the electric motor 1202 described in the JP-A-2002-321665 which is provided on the vehicle 1201 for driving the same, however, depending upon load, there may occur a case where the length of the bearing portion 1206 into which the bearing 1205 is fitted is increased. The bearing 1205 is a single-row bearing, but for example, in the event that the bearing 1205 is modified from the single-row bearing to a double-row bearing to match a condition such as load, the width of the bearing becomes large (thick), whereby the output shaft 1203 is elongated and the motor case 1207 is enlarged. There has been a demand for a decrease in the width of a double-row bearing for supporting an output shaft of an electric motor for driving a vehicle.